Adaptive defrost

ABSTRACT

Adaptive defrost systems, computer program products, and methods are provided. A defrost cycle is initiated, and an actual time of defrost (TOD) is determined based on the defrost cycle. Additionally, a first time between defrost (TBD) between defrost cycles is determined. A variable increment time between defrost (TBDInc) is calculated based at least partially on the ideal time of defrost and the actual time of defrost. The TBD is incremented by TBDInc, resulting in a new TBD, which may be used to initiate the next defrost cycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to co-pending U.S. Provisional Patent Application No. 61/829,652, filed on May 31, 2013, which is hereby incorporated by reference by its entirety.

BACKGROUND

Devices, such as refrigerators or freezers, include a refrigeration unit and a defrost heater. The defrost heater is cycled on the basis of electromechanical timers which accumulate time on the basis of compressor run time. When the timer accumulates a predetermined amount of compressor run time, the defrost heater initiates a defrost cycle, regardless of the current state of various refrigeration components and environment. This can lead to an inefficient use of energy.

SUMMARY OF INVENTION

Embodiments of the invention relate generally to the control of a defrost heater for a refrigerator and specifically to an adaptive control method and apparatus therefor. According to some aspects, a method, a control mechanism, and a refrigerator implementing adaptive defrost is provided. In this regard, a defrost cycle is initiated, and an actual time of defrost (TOD) is determined based on the defrost cycle. Additionally, a first time between defrost (TBD) between defrost cycles is determined. A variable increment of time between defrost (TBDInc) is calculated based at least partially on the ideal time of defrost and the actual time of defrost. The TBD is incremented by TBDInc, resulting in a new TBD, which may be used to initiate the next defrost cycle.

BRIEF DESCRIPTION OF DRAWINGS

Aspects of the present invention are further described in the detailed description which follows in reference to the noted plurality of drawings by way of non-limiting examples of embodiments of the present invention in which like reference numerals represent similar parts throughout the several views of the drawings and wherein:

FIG. 1 is a perspective view of a refrigerator embodying an adaptive defrost control according to one aspect of the present invention;

FIG. 2 is a schematic view of a refrigerator embodying the adaptive control according to one aspect of the present invention;

FIG. 3 illustrates a method of adaptive defrost in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

As discussed in more depth below, embodiments of the present disclosure relate to adaptive defrost, such as control of a defrost heater in a refrigeration device. Adaptive defrost relates, according to some embodiments, to variably changing a time to increment the defrost cycle of a cooling device based on certain parameters. The defrost time is adaptive so that the time to defrost (or the time which the defrost heater is on) is not activated more often than necessary. This allows efficiency of a defrost circuit of a refrigeration device.

It should be understood that the present disclosure is applicable to refrigeration devices, such as a refrigerator, freezer, or any other device which uses a compressor to cool an area. It is noted that some embodiments of the present disclosure are described with regard to describing the operation of a refrigerator for ease of illustration and description. It should be understood, however, that the present disclosure should not be so limited and any other type of refrigeration device is within the scope of the present disclosure.

FIG. 1 illustrates a refrigerator 100 having a cold compartment 102. The cold compartment could be a freezer or refrigerator compartment. The cold compartment 102 may be provided with a door 103 (or other opening member) configured to activate a switch (not shown) which monitors the condition of the door 103 to determine if the door is either open or closed.

FIG. 2 illustrates a block diagram illustration of the refrigerator 100 of FIG. 1. The refrigerator 100 comprises an adaptive defrost controller 210, a compressor 212, and a defrost controller 214. The defrost controller 214 is provided to defrost the cold compartment 102 of the refrigerator 100 and may include a defrost heater and defrost thermostat.

The adaptive defrost controller 210 may be programmed to control activation and deactivation of the defrost heater in accordance with the embodiments discussed below. In a sense, the adaptive defrost controller 210 determines the time between defrost (“TBD”) or the time when the defrost heater is off. Additionally, the adaptive defrost controller 210 may identify or monitor the time of defrost (“TOD”) or the time when the defrost heater is on.

However, the adaptive defrost controller 210 is also programmed to adjust the value of the time between defrost based upon certain operating conditions. In order to reduce the above-described inefficient use of energy, the adaptive defrost controller 210 monitors the time of defrost and adjusts the time between defrost accordingly. Accordingly, the adaptive defrost controller 210 calculates the time between defrost using an algorithm, an example of which is illustrated in FIG. 3.

The adaptive defrost controller 210 may include a processor 202, memory 204, and an adaptive control module 206. The processor 202 may be configured to perform any of the steps discussed herein and in FIG. 3 to perform adaptive defrost. The memory 204 is configured to store computer readable instructions as well as any data and preset variables, such as the variables discussed below with respect to blocks 302 and 304. The adaptive controller module 206 may include the computer instructions which may perform the steps of FIG. 3. The adaptive defrost controller 210 may be configured to communicate with other components of the refrigerator, such as the defrost controller 214 (e.g., defrost thermostat, the defrost heating member, etc.), thermostats (e.g., refrigerator thermostat 208 and freezer thermostat 209), any timers, the compressor 212 and the like. In this regard, the adaptive defrost controller may operate as a control to operate when the compressor and/or defrost cycle activates and deactivates.

The algorithm shown in FIG. 3 illustrates one embodiment for adjustments of the time between defrost according to one aspect. In block 302, the minimum cumulative compressor run time (MinTBD) is established between defrost cycles through testing or review of existing tests, such as about 8 to 12 hours. Additionally, a maximum cumulative compressor run time (MaxTBD) is established between defrost cycles from product testing, such as about 96 hours, and a maximum compressor continuous run time (MaxComOn) is established, such as about 4 to 6 hours to indicate heavy usage and to act as a signal to limit the time between defrosts to a minimum. In block 304, an ideal time of defrost (ITOD) is established, such as any time between about 15 to 25 minutes (e.g., 21 minutes). In block 306, the time between defrost (TBD) may be initially set to a predetermined value, such as the MinTBD. The minimum run time, maximum run time, maximum compressor continuous run time, time between defrost, and/or ideal time of defrost may be preset by the manufacturer prior to operation of the refrigerator. In this regard, these values may be predetermined and set for the refrigerator prior to regular residential or commercial use of refrigerator.

The refrigerator may begin operation by the user, as provided by block 308. In other words, the refrigerator is powered on and the compressor runs to cool the medium or area as intended. Two timers are activated: a cumulative compressor run time timer and a continuous compressor run time timer. The cumulative compressor run time timer records the cumulative time that the compressor has run since the last defrost cycle. The continuous compressor run time timer records the continuous run time of the compressor since the last defrost cycle indicating how long the compressor has been continuously running since it was last turned on.

In block 310, the cumulative compressor run time is recorded. Also shown in block 310, a separate timer (i.e., the continuous compressor run time timer) is also activated each time the compressor starts to monitor the continuous compressor run time (i.e., the amount of time that the compressor has been continuously running). The continuous compressor run time is compared to a maximum value to be an indicator of heavy compressor usage.

The refrigeration process is discussed in more depth below.

The refrigerator produces a controlled heat transfer by the evaporation in an evaporator chamber of a liquid refrigerant under pressure conditions which produce the desired evaporation temperatures. The liquid refrigerant absorbs its latent heat of vaporization from the medium being cooled (e.g., the cold compartment 102) and, in this process, is converted into a vapor at substantially the same pressure and temperature. This vapor has its temperature and pressure increased by a compressor and is then conveyed into a condenser chamber in which the pressure is maintained at a substantially constant level to condense the refrigerant at a desired temperature. The quantity of heat removed from a refrigerant in the condenser is the latent heat of condensation plus the super heat which has been added to the vapor refrigerant in the process of conveying the refrigerant from the evaporator pressure level to the condenser pressure level. After condensing, the liquid refrigerant is passed from the condenser through a suitable throttling device back to the evaporator to repeat the cycle.

In a closed cycle system, generally a mechanical compressor or pump is used to transfer the refrigerant vapor from the evaporator (low pressure side) to the condenser (high pressure side). The vaporized refrigerant drawn from the evaporator is compressed and delivered to the condenser wherein it undergoes a change in state from a gas to a liquid transferring heat energy to the condenser cooling medium. The liquefied refrigerant is then collected in the condenser or in a separate receiver and fed back to the evaporator through the throttling device.

Evaporators have the primary objective of affording easy transfer of heat from the medium being cooled to the evaporating refrigerant. In one type of evaporating system (direct expansion), refrigerant is introduced into the evaporator through a thermal expansion valve and makes a single pass in thermal contact with the evaporator surface prior to passing into the compressor suction line.

While the evaporator functions to collect refrigerant to pass from a liquid state into a vapor state extracting the latent heat of vaporization of the refrigerant from the surrounding medium, the function of the condenser is the reverse of the evaporator, i.e. to rapidly transfer heat from the condensing refrigerant to the surrounding medium.

When in the cooling mode the evaporator coil is prone to a build-up of frost because water vapor condenses on the evaporator and may freeze. Such frost, or eventually ice, can substantially decrease the efficiency of the unit, and therefore defrost cycles are typically applied to remove the condensate/ice. A defrost cycle can be accomplished by reversing the flow of refrigeration through the system so as to circulate a heated fluid through the evaporator coil. It may also be accomplished with the use of an electrical resistance heater. After each periodic defrost cycle, the temperature control unit is returned to operate in the cooling mode until the build-up of condensation again requires a defrost cycle.

Referring back to FIG. 3, in block 312, the refrigerator system determines if the continuous compressor run time is greater than the maximum compressor on time (MaxComOn). If so, the TBD is set to be MinTBD so that the defrost may be performed under heavy usage conditions. Otherwise, the method may continue to blocks 311 and 313.

In block 311, a determination is made as to whether the compressor is off. If not, the method may continue to block 316 (discussed below); otherwise, the method may continue to block 313 where the method may wait until the compressor turns back on. When the compressor does turn back on (in block 313), the continuous compressor run time timer is reset in block 315 and the method then may proceed to block 316. In this regard, blocks 311 and 313 effectively determine when the continuous compressor run time timer should be reset, such as when the compressor is turned off and then turned back on.

In block 316, a determination (which was started at block 310) is made as to whether the cumulative compressor run time timer (also referred to herein as the TBD timer) has reached TBD. If not, the method may proceed back to block 312; otherwise, if the timer has reached TBD, the system determines that the defrost cycle should be initiated and runs the defrost cycle in block 318. At this point, a heating member (e.g., resistor, heating fluid, etc.) heats the evaporator coil until the defrost thermostat or other temperature measuring device reaches a predetermined temperature. When the defrost thermostat reaches such predetermined temperature, the heating member ceases to heat the evaporator coil and the defrost cycle may end. Alternately, other control means may monitor the temperature of the evaporator coil and terminate the defrost cycle.

In block 320, the time of defrost (TOD) is determined. While the defrost cycle is in operation, a defrost timer is initiated to monitor the time of defrost (TOD) according to one embodiment. The system saves the determined TOD from the defrost timer and saves such value into memory. Any previously saved TOD value is replaced with the newly-determined TOD from the defrost timer. In one embodiment, the TOD is any time between about 10 to 30 minutes.

In block 322, an adaptive increment (TBDInc) to the TBD is calculated by the adaptive defrost controller. TBDInc may be a value which allows the adaptive defrost controller to iteratively determine the precise amount of time of defrost needed by the refrigerator. This may be performed by an algorithm which may be stored in the above-described non-transitory computer readable medium. In one embodiment, the TBDInc is calculated the minimum of a preset maximum (X) or the following equation:

TBDInc=((ITOD−TOD)/ITOD)*Factor

Where ITOD is the preset ideal time of defrost (as discussed with regard to block 302), TOD is the determined time of defrost (discussed in block 320), and “Factor” is a variable defined to make suitable adjustments based on previous testing and may differ if TOD is smaller than or larger than ITOD. The preset maximum (X) may be a number of maximum hours that the TBDInc should not exceed, e.g., any amount of hours between 2 hours and 10 hours such as about 6 hours. For example, if ITOD is 15 minutes, TOD is determined to be 10 minutes, X is 6 hours, and the “Factor” is 15, TBDInc is determined by the adaptive defrost controller to be 5 hours.

As previously noted, if the calculated TBDInc is greater than a preset maximum (X), TBDInc may be set to X. This allows TBDInc to have a maximum positive amount to increment TBD.

The adaptive defrost controller compares TBD+TBDinc relative to MinTBD (block 324) and MaxTBD (block 328). If TBD+TBDinc is less than MinTBD, in block 326, the adaptive defrost controller sets TBD to be MinTBD. However, if TBD+TBDinc is greater MaxTBD, the adaptive defrost controller sets TBD to be MaxTBD, as shown in block 330. If TBD+TBDinc is greater than or equal to MinTBD but less than or equal to MaxTBD, the adaptive defrost controller sets TBD to be TBD+TBDinc as shown in block 332. After either block 326, block 330 or block 332 is completed, the method may proceed back to block 310 where the compressor run time timer and the TBD timer are reset and restarted. The method may then continuously run so that the defrost cycle eventually may evolve toward the ideal time of defrost.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowcharts and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to embodiments of the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of embodiments of the invention. The embodiment was chosen and described in order to best explain the principles of embodiments of the invention and the practical application, and to enable others of ordinary skill in the art to understand embodiments of the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that embodiments of the invention have other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of embodiments of the invention to the specific embodiments described herein. 

What is claimed is:
 1. A method for adaptive defrost comprising: initiating a defrost cycle; determining an actual time of defrost (TOD) of the defrost cycle; determining a first time between defrost (TBD) as a time period for which a compressor should be operated between defrost cycles; calculating, by a computer, a variable increment time between defrost (TBDInc) based at least partially on a preset ideal time of defrost (ITOD) and the actual time of defrost, the increment time between defrost being a time to adjust the first TBD; incrementing the first TBD by TBDInc, resulting in a second TBD; and initiating a defrost cycle after the second TBD has elapsed.
 2. The method of claim 1, wherein the calculating the TBDInc comprises calculating the TBDInc using the following equation: ((ITOD−TOD)/ITODrfactor), where the factor comprises a constant value.
 3. The method of claim 1, wherein the calculating the TBDInc comprises calculating the TBDInc based on TOD and the ITOD.
 4. The method of claim 1, wherein the calculating the TBDInc comprises calculating the TBDInc by subtracting the TOD from the ITOD and then dividing the ITOD.
 5. The method of claim 1, further comprising setting the second TBD to be a minimum desired TBD in response to a run time of the compressor being greater than a maximum set value.
 6. The method of claim 1, wherein the TOD comprises a time period where a defrost heater is activated.
 7. The method of claim 1, further comprising setting the second TBD to be a minimum desired TBD in response to the second TBD being less than the minimum desired TBD.
 8. The method of claim 1, further comprising setting the second TBD to be a maximum desired TBD in response to the second TBD being greater than the maximum desired TBD.
 9. A control mechanism in a refrigerator configured for removing frost by a method comprising: initiating a defrost cycle; determining an actual time of defrost (TOD) of the defrost cycle; determining a first time between defrost (TBD) as a time between defrosting cycles; calculating, by a computer, a variable increment time between defrost (TBDInc) based at least partially on a preset ideal time of defrost (ITOD) and the actual time of defrost, the increment time between defrost being a time to adjust the first TBD; incrementing the first TBD by TBDInc, resulting in a second TBD in response to the second TBD being less than a maximum desired TBD but greater than a minimum desired TBD; and initiating a defrost cycle after the second TBD has elapsed.
 10. The control mechanism of claim 9, wherein the method further comprises setting the second TBD to be a maximum desired TBD in response to the second TBD being greater than the maximum desired TBD.
 11. The control mechanism of claim 9, wherein the method further comprises setting the second TBD to be a minimum desired TBD in response to the second TBD being less than the minimum desired TBD.
 12. The control mechanism of claim 10, wherein the calculating the TBDInc comprises calculating the TBDInc based on TOD and the ITOD.
 13. A computer program product embodying a instructions that, when executed on a computer, cause the computer to perform a method, the method comprising: initiating a defrost cycle; determining an actual time of defrost (TOD) of the defrost cycle; determining a first time between defrost (TBD) as a time between defrosting cycles; calculating a variable increment time between defrost (TBDInc) based at least partially on a preset ideal time of defrost (ITOD) and the actual time of defrost, the increment time between defrost being a time to adjust the first TBD; incrementing the first TBD by TBDInc, resulting in a second TBD; and initiating a defrost cycle after the second TBD has elapsed. 